Population shifts and potential function of size-fractioned microbes along the twilight zone

POC sinking export efficiency was related to the difference of ocean net primary production and phytoplankton community structure, these differences might lead to changes in the composition and function of microbial communities in the twilight zone. In the present study, a large-volume in situ water transfer system was applied to enrich microbes associated with POC in the upper and lower boundary of the twilight zone of three contrasting environments (the oligotrophic waters, cold seeps and hydrothermal vents), with those from the euphotic layer for a comparison. Metagenomic study and bioinformatic analysis were used to uncover composition and metabolic function of the microbial community associated with particles, and MAGs was obtained to reconstruct the metabolic potential of the microbiome. The objective of this study was to better understand the shifts and connectivity of microbial communities, especially their metabolic capabilities in terms of degradation, aggregation and transformation of organic matter occurred in the twilight zone.